Not Applicable.
Not Applicable
This invention relates to an equalization system, and more particularly, to a system for use in an optical network to correct for unequal gain of power in the channels of the optical signal.
The transmission, routing and dissemination of information has occurred over computer networks for many years via standard electronic communication lines. These communication lines are effective, but place limits on the amount of information being transmitted and the speed of the transmission. With the advent of light-wave technology, a large amount of information is capable of being transmitted, routed and disseminated across great distances at a high transmission rate over fiber optic communication lines.
When information is transmitted over fiber optic communication lines, impairments to the pulse of light carrying the information can occur, including pulse broadening (dispersion) and attenuation (energy loss). In-line amplifiers spaced throughout the fiber optic communication system boosts the power of each channel of the optical signal to assist in the compensation of the energy lost during transmission. The in-line amplifiers boost each channel of the optical signal with the same amount of power. However, as different wave lengths of light are used over the different channels of the fiber optic communication system, the amount of energy lost per channel is not consistent. As the in-line amplifier boosts the energy across all channels of the optical signal transmitted over the fiber optic communication system, the power gain of any specific channel may fail to meet or exceed the desired power gain. Further, energy loss caused by polarization dependent loss (PDL) lead to further nonuniform power gain over the multiple channels of the optical signal transmitted over the fiber optic communication system.
As the optical signal is transmitted across the fiber optic communication system, the gain differences on a channel-by-channel basis accumulate. These gain differences can cause distortions of the optical signal shape and therefore lead to performance degradation. Current systems allow for the optical signals"" power deviations to accumulate before they are compensated by the gain equalizer after analysis by the optical spectrum analyzer (xe2x80x9cOSAxe2x80x9d). Inherent in these systems is a process which allows a large amount of gain differences to accumulate prior to equalization. Prior to the gain equalization of the channels of the optical signal, the optical signal performance begins to degrade and thus the overall performance of the fiber optic communications system is degraded.
To compensate for gain differences in the multiple channels of the optical signal, gain equalizers are provided, spaced periodically, throughout the fiber optic communication lines (see FIG. 1). The gain equalizers equalize the power at the in-line amplifiers on a channel-by-channel basis throughout the optical signal. To determine the amount of gain on a channel-b-channel basis, an optical spectrum analyzer is co-located with the gain equalizer. The Optical measures the power level associated with each channel of the optical signal and compares this power level with the desired power level for each channel and provides this information to the gain equalizer which is co-located with the Optical spectrum analyzer at an in-line amplifier within the fiber optic communication system. The gain equalizer then equalizes the power of each channel based upon the analysis performed by the Optical spectrum analyzer at this in-line amplifier location. As can be seen in FIG. 2, the gain equalizer zeroes out the gain differences throughout the channels at the point in the fiber optic communication system where the gain equalizer and Optical spectrum analyzer are located. Therefore, any advancement in the ability to lower the amount of gain difference accumulated during the transmission of information over a fiber optic communication system would be advantageous.
A power equalization system and method for use in an optical transmission system are provided. The power equalization system includes an optical line including at least one transmission channel and a management line. The transmission system further includes a plurality of amplifiers, a plurality of Optical spectrum analyzers and a plurality of equalizers. The plurality of amplifiers are coupled to the optical line, spaced periodically throughout the optical transmission system. As information is sent through the optical transmission system, the plurality of amplifiers boost the power of each channel of the optical signal. A plurality of Optical spectrum analyzers are also coupled to the optical line and are spaced periodically throughout the optical transmission system and are co-located with a first portion of the amplifiers coupled to the optical line. A plurality of equalizers are also coupled to the optical line and are spaced periodically throughout the optical transmission system and equalize the power on each channel of the optical line. The plurality of equalizers are co-located with a second portion of the plurality of amplifiers and at least one of the plurality of Optical spectrum analyzers is not co-located with one of the plurality of equalizers. Thus, as the optical information is transmitted over the optical transmission system, the Optical spectrum analyzers provide analysis data via the management line to the non co-located equalizers for use by the equalizers in equalizing the power of the channels of the optical line at that point. The analysis data generated by the Optical spectrum analyzer identifies the analysis data at the point of the Optical spectrum analyzer which is not co-located with the equalizer.